Torsional vibration damper

ABSTRACT

A vibration damper assembly operatively connecting a driving pulley with an automotive engine output shaft which drives a serpentine belt system with an automatic belt tensioner. The vibration damper assembly serves to dampen torsional, bending, and transitional vibrations transmitted from the output shaft through the poly-V belt and engine frame to the belt tensioner. The vibration damper assembly . .comprises.!. .Iadd.includes .Iaddend.a mounting element, fixed to the output shaft, in torsional transmitting relation therewith, bearing member operatively disposed between the driving pulley and the mounting element to restrict relative movement therebetween to torsional relative movement, and a resilient member operatively connected between the driving pulley and the mounting element in resilient torsional transmitting relation therebetween.

This invention relates generally to serpentine belt systems forautomotive vehicles and more particularly to vibration dampingimprovements for extending the useful life of the belt tensioner of thesystem.

In recent years, it has been found desirable to replace the conventionalmultiple individual belt system with a system embodying a single beltarranged in serpentine fashion to drive all of the multiple rotaryinstruments heretofore driven by separate belts. Most of the singleserpentine belt systems thus far utilized have included a separate belttensioning device both as an essential to the proper functioning of thesystem and as a means to simplify the mounting and tensioning of thebelt in operative relation therewith.

A common type of belt tensioner embodies a fixed structure and a pivotedstructure in the form of an arm carrying a belt engaging pulley pivotedto the fixed structure by a pivot assembly. A coil spring is mountedbetween the fixed structure and the pivoted structure and has its endsconnected between the fixed and pivoted structures so as to bias thelatter into tensioning engagement with the poly-V belt to maintain thepoly-V belt in driven engagement with the driving pulleys and in drivingengagement with the driven pulleys. It can be appreciated that long-termoscillations of the belt tensioner arm about its pivotal axis can have adeleterious effect on the interaction of components within the tensionerand the ability of the tensioner mechanism to maintain constant tensionwithin the poly-V belt.

While belt tensioners are well-known devices and have been utilized inmany belt systems, the requirements placed upon belt tensioners utilizedin serpentine single belt automotive systems are particularly stringent.These requirements stem from a combination of factors including therelatively greater belt length utilized and hence the relatively greaterbelt take-up capacity required. In addition, significant wear of thebelt tensioner is caused by extensive oscillations of the tensionerabout its pivotal axis as a result of vibrations, resultant from varyingrotational speed of the engine, imparted to the tensioner through theengine crankshaft, poly-V belt and engine frame. Such vibrations include"torsional" vibrations caused by twisting of the crankshaft inconjunction with the firing pressures of the pistons every combustioncycle, and "bending" vibrations of the crankshaft caused by momentarydeflections of the crankshaft in response to such firing pressures.These vibrations reach particularly high levels when the naturalfrequencies of the crankshaft/poly-V belt/pulley system match the highamplitude of the engine firing forces over the normal operating speed ofthe engine. In addition, instantaneous tightening and loosening of thepoly-V belt resulting from the changing rotational speeds of thecrankshaft causes harmful "transitional" vibrations to be imparted tothe belt tensioner. Therefore, there exists a need for a serpentine beltsystem having a torsional/bending/transitional vibration damper(hereinafter termed torsional vibration damper for simplicity) whichwill effectively address the aforementioned problems and enable the belttensioner to function properly over an extended period of time.

It is an object of the present invention to fulfill the need expressedabove. In accordance with the principles of the present invention, thisobjective is achieved by providing the combination including an internalcombustion engine having an engine frame and an output shaft rotatableby operation of the internal combustion engine, the output shaft beingsubject to torsional and bending vibrations resulting from the operationof the internal combustion engine. In the combination, a plurality ofdriven shafts are mounted for rotational movement about parallel axesfixed with respect to the engine frame, and a plurality of drivenpulleys are operatively connected with the driven shafts. A drivingpulley is operatively connected with the output shaft. An endlessflexible poly-V belt is trained about the driven and driving pulleys,the poly-V belt being subject to transitional vibrations from changingrotational speeds of the crankshaft. The combination further comprises abelt tensioner carried by the engine frame in tensioning engagement withthe poly-V belt for maintaining the poly-V belt in driven engagementwith the driving pulley and in driving engagement with the drivenpulleys. Finally, a vibration damper assembly is provided to operativelyconnect the driving pulley with the output shaft for damping thetorsional vibrations, the bending vibrations, and the transitionalvibrations transmitted from the output shaft through the poly-V belt andthe engine frame to the belt tensioner. The vibration damper comprises amounting element, fixed to the output shaft, in torsional transmittingrelation therewith, .Iadd.a mass element annularly disposed about theoutput shaft and fixed to the mounting element via an elastic dampingelement, .Iaddend.a bearing means operatively disposed between thedriving pulley and the mounting element to restrict relative movementtherebetween to torsional relative movement, and a resilient memberoperatively connected between the driving pulley and the mountingelement in resilient torsional transmitting relation therebetween.

Since rotation of the output shaft, in conjunction with the drivingpulley and poly-V belt, rotationally drives the driven pulleys anddriven shafts, the driven shafts also become a source of torsional,bending, and transitional vibrations. Therefore, the aforementionedproblems of the belt tensioner can be further alleviated by providing adamping assembly on the driven shafts as well.

It is a further object of the invention to provide a back-up means forproviding torsional transmission between the mounting element and thedriving pulley in the event that the resilient member fails in itstorsional transmission.

These and other objects of the present invention will become moreapparent during the course of the following detailed description andappended claims.

The invention may best be understood with reference to the accompanyingdrawings wherein illustrative embodiments are shown.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view of a torsional vibration damperembodying the principles of the present invention.

FIG. 2 is a lefthand side elevational view of the torsional vibrationdamper shown in FIG. 1.

FIG. 3 is a schematic view of an automotive internal combustion engineserpentine belt system including a torsional vibration damper embodyingthe principles of the present invention.

FIG. 4 is an overhead schematic view of the belt tensioner shown inFIG. 1. FIG. 5 is a vertical sectional view of a second embodiment ofthe torsional vibration damper of the present invention.

Referring now more particularly to FIG. 1 of the drawings, there isshown therein a torsional vibration damper, generally indicated at 10,which is constructed in accordance with the principles of the presentinvention. As shown, the torsional vibration damper 10 includes amounting element or hub 12 adapted to be mounted on the forward end ofan engine crankshaft 14 and which serves as a mount for a pulley,indicated generally at 16, and provides an axis of rotation. Hub 12 issecured to crankshaft 14 by means of a bolt 15 and has a radiallyextending annular wall portion 18 integrally connecting two concentricaxially outwardly extending. cylindrical portions 20 and 22. As can beappreciated, generally indicated at 17 is a conventional key/keywayassembly for predetermining the fixed angular position of the torsionalvibration damper on the crankshaft 14. Cylindrical portion 20 isdisposed radially inward from cylindrical portion 22 and has an innersurface 24 which is adapted to be mounted to crankshaft 14 and an outersurface 26 which serves as a seat for a bearing element 28. Cylindricalportion 22 includes an inner peripheral cylindrical surface 30 and anouter surface 32. A resilient member 34 is annularly disposed aboutcylindrical portion 22. While resilient member 34 is preferably made ofrubber, any elastomer may be used. Rings 31 and 33 made of a rigidmaterial, preferably metal, are respectively disposed about the innersurface 37 and outer surface 39 of resilient member 34. While rings 31and 33 made of relatively rigid material are compression fitted aboutresilient member 34 by compression of resilient member 34 between therings, the rings may also be fixed to the resilient member by bonding ofthe resilient member at the metal-rubber interface.

A cylindrical poly-V belt engaging portion 38, having an inner surface36, of pulley 16 is disposed about ring 33. Inner surface 36 istorsionally fixed to ring 33 just as outer surface 32 of cylindricalportion 22 is torsionally fixed to ring 31.

Another alternative method of torsional fixing of resilient member 34 tocylindrical portions 22 and 38 is either mechanical, chemical, thermalor thermochemical bonding directly to surface 32 and 36.

Pulley 16 has an outer peripheral cylindrical surface having a poly-Vconfiguration 44 adapted to engage endless flexible poly-V belt 46.Pulley 16 includes radially extending annular disk portion 40, extendingradially inwards from and integrally connecting cylindrical poly-V beltengaging portion 38 with cylindrical bearing engaging portion 42.Bearing engaging portion 42 extends from disk portion 40 axiallyinwardly between cylindrical portions 20 and 22 of hub 12 and rests uponbearing element 28.

Hub 12 receives torsional rotation from crankshaft 14 as a result of theoperation of an internal combustion engine. Resilient member 34, whichis operatively connected between hub 12 and pulley 16 resilientlytransmits torsional rotation from hub 12 to pulley 16. Bearing element28 restricts relative movement between pulley 16 and hub 12 to torsionalrelative movement. It can be appreciated, however, that the relativemovement between hub 12 and pulley 16 is rather slight and occurs mostlywhen there is large transitions in the operating speed of output shaft14. During such transitions, resilient member 34 effectuates what maybedeemed a slight rotational "lag" of the pulley 16 with respect to thehub 12 so as to alleviate the yanking or transitional vibratory effecton poly-V belt 46. Resilient member 34, operating in conjunction withbearing element 28 also serves to absorb torsional vibrations of shaft14 transmitted through hub 12. As a result, poly-V belt 46 is furtherrelieved of these vibrations.

Cylindrical portion 22 has a protruding portion 48 which protrudesthrough slot 50 in disk portion 40 of pulley 16. As shown more clearlyin FIG. 2, slot 50 has an edge 52. Protruding portion 48 is held in aspatially separated relation from side portions 54 of edge 52 byresilient member 34. Even accounting for the lag between pulley 16 andhub 12 during high acceleration or deceleration of output shaft 14,protruding portion 48 is prevented from engaging side portions 54.However, in instances of failure of resilient member 34, such as acracking or tearing, protruding portion 48 is permitted to engage sideportions 54 so that hub 12 continues to be in torsional transmittingrelation with pulley 16. In effect, protruding portion 48 in conjunctionwith edge 52 of slot 50 serves as a direct drive back-up shouldresilient member 34 fail.

Referring now back to FIG. 1, a mass element 53 is shown annularlydisposed about hub 12 and is connected thereto by a radially extendingannular retaining element 56. Retaining element 56 may be integrallyformed with hub 12, but in the most preferred embodiment, retainingelement 56 is fixed to hub 12 by bolts 58 (only one bolt is shown in thefigure). Similarly, while mass element 53 may be formed integral withhub 12 and/or retaining element 56, in the described embodiment, aradially extending elastic member 60, preferably made of rubber,adhesively secures mass element 53 with retaining element 56. Thiselastic member 60 in conjunction with mass element 53 is used for tuningthe dampening of engine crankshaft bending vibration that is caused byfiring pressure on engine pistons during combustion cycles. It can beappreciated that the specific configuration of elastic member 60 isoperable to tune bending vibrations. As elastic member 60 is shiftedfrom its radially extending configuration to an axially extendingconfiguration, however, (for example, see elastic member 362 in FIG. 5),less bending vibrations are damped, and torsional vibrations are thenprimarily tuned and damped. The damping of such vibrations not onlyreduces torsional . .and.!. .Iadd.stresses but also reduces.Iaddend.bending stresses within the crankshaft during operation of thecombustion engine.

Referring now to FIG. 3 an automotive internal combustion engine,generally indicated at 110, which includes an engine frame 112 andcrankshaft 14. Fixed to the crankshaft 14 is pulley 16 forming a part ofa serpentine belt system, generally indicated at 118. The belt system118 includes an endless poly-V belt 46. The poly-V belt 46 is of thethin flexible type. The poly-V belt 46 is trained about the pulley 16and a plurality of further pulleys 122, 124, 126, 128, and 130 each ofwhich is fixed to respective shafts 132, 134, 136, 138 and 140. Theshafts are connected to operate various engine accessories. For example,shaft 132 drives a water pump, shaft 134 a power steering pump, shaft136 an alternator, shaft 138 an air injection pump, and shaft 140 acompressor of an air conditioning system for the automobile utilizingthe engine 110.

It will be understood that the internal combustion engine 110 may be ofany known construction. In accordance with conventional practice, theoperation of the engine is such as to impart vibratory forces to theengine frame 112. All of the accessories are mounted on the engine frame112 so that the shafts are rotated about parallel axes which are fixedwith respect to the engine frame 112 and parallel with the output shaft16 thereof.

The poly-V belt 46 is tensioned by a belt tensioner, generally indicatedat 142. The belt tensioner 142 is also mounted on the engine frame 112.It will be understood that the engine frame 112 is mounted on thechassis of the automotive vehicle through appropriate shock absorbingmounts which serve to isolate the vibratory forces which are establishedby the operation of the internal combustion engine from the vehicleframe but not from the engine frame. The torsional vibratory forceswhich are established by the operation of the internal combustion engine110 and torsional rotation of crankshaft 14 to which the pulley 16 issubjected are transmitted to the belt tensioner 42 through poly-V belt120. In addition, momentary deflections of the crankshaft 14 may beimparted to the belt tensioner 142 through vibrations of the engineframe 112 itself.

Referring more particularly to FIG. 4 of the drawings, the belttensioner 142 of the present invention includes a fixed structure 236which is adapted to be secured, via bolt 256, to a bracket plate 238 orthe like in a stationary position with respect to the engine block. Thebelt tensioner also includes a pivoted structure 240 which is mountedwith respect to the fixed structure 236 for a pivotal movement about afixed pivotal axis, indicated by phantom line 250. The pivoted structure240 carries a belt engaging tensioner pulley 242 for rotational movementabout rotational axis indicated at phantom line 252, parallel with thepivotal axis. A coil spring 244 is mounted between the fixed structure236 and pivoted structure 240 for resiliently biasing the latter to movein a direction towards poly-V belt 46 so as to maintain tensioner pulley242 in tensioning engagement with poly-V belt 46. Belt tensioner 142maintains poly-V belt 46 in driven engagement with driving pulley 16 andin driving engagement with driven pulleys 122, 124, 126, 128, and 130.

As noted previously, pivoted structure 240 is subject to oscillatorymovement about its pivotal axis 250 as a result of torsional, bending,and transitional vibrations transmitted from output shaft 14 throughpoly-V belt 46 and the engine frame 112. The vibration damper of thepresent invention significantly helps reduce such oscillatory movementand prolong the life of belt tensioner 142.

FIG. 5 is a vertical sectional view of another embodiment of thetorsional vibration damper of the present invention. The function ofthis embodiment is quite similar to that of the embodiment depicted inFIG. 1, and will now be described in greater detail. The torsionalvibration damper, generally indicated at 310, includes a stamped hub 312which operates to mount the torsional vibration damper to enginecrankshaft 314. As can be appreciated, generally indicated at 315 is aconventional key/keyway assembly for predetermining the fixed angularposition of the torsional vibration damper on the shaft. The axialextremity of crankshaft 314 comprises an annular flat face 316, and acentral protruding portion 318 which protrudes from the center ofannular flat face 316. Protruding portion 318 has a peripheral radialwall 320, which together with flat face 316 forms a seat for stamped hub312. Protruding portion 318 has an inner threaded bore 322 which isadapted to receive threads 324 of bolt 326.

Bolt 326 passes through a cup member 328 and a retaining washer 330.Retaining washer 330 bears against the inner surface 332 of cup member328, while the outer surface 334 of cup member 328 comes into contactwith stamped hub 312 at a portion thereof generally indicated at 336.Bolt 326 is tightly screwed to crankshaft 314 so as to compressretaining washer 330, cup member 328, and stamped hub 312 therebetween.

A resilient member 340 is secured between two concentrically disposedouter and inner rings 342 and 344 similar to the configuration asdescribed in FIG. 1. Rings 344 and 342 are secured respectively to anouter peripheral surface 345 of cup member 328 and an inner surface 347of a pulley 346, which is adapted to engage endless flexible poly-V belt348. Pulley 346 includes radially extending annular disk portion 350,extending radially inwards from the portion at which pulley 346 engagespoly-V belt 348 and towards a bearing engaging portion 352. Bearingelement 354 is disposed between bearing engaging portion 352 and aninner portion 353 of stamped hub 312 which engages radial wall 320 ofcrankshaft 314. In this embodiment, stamped hub 312 has a portionthereof constituting a protruding portion 356, which is held inspatially separated relation from side portions 358 as similarlydisclosed in the description of FIG. 2 with respect to side portions 54and protruding portion 48.

An upper portion 360 of stamped hub 312 has an elastic member 362 bondedthereto. Elastic member 362 substantially corresponds to elastic member60 in the first embodiment Mass element 364 substantially corresponds tomass element 54 in the first embodiment, and is resiliently attached tostamped hub 312 through elastic member 362.

As crankshaft 314 rotates, stamped hub 312, cup member 328, retainingwasher 330, and bolt 326, which are all tightly secured thereto, rotatein unison therewith. As cup member 328 receives torsional rotation fromcrankshaft 314 as a result of the operation of an internal combustionengine, resilient member 340 resiliently transmits torsional rotation topulley 346. Bearing element 354 restricts relative movement betweenpulley 346 and cup member 328 to torsional relative movement. It can beappreciated, however, that the relative movement between cup member 328and pulley 346 is rather slight and occurs mostly when there is largetransitions in the operating speed of output crankshaft 314. During suchtransitions, resilient member 340 effectuates the same type of lagaccomplished by resilient 34 in the first embodiment. Resilient member340, operating in conjunction with bearing element 354 also serves toabsorb torsional vibrations of shaft 314 transmitted through stamped hub312. And, in instances of failure of resilient member 340, protrudingportion 356 of stamped hub 312 is permitted to engage side portions 358so that stamped hub 312 becomes in torsional translating relation withpulley 346.

Finally, it can be appreciated that while the vibration dampingassemblies in FIGS. 1 and 5 are shown attached to output shaft 14, theycan just as easily be attached to any one or more of the driven shaftsshown in FIG. 3. Each accessory driven by the respective driven shafthas its specific natural frequency and dynamic characteristic influencedby the rotational inertia, pulley system geometry, etc. Providing atorsional vibration damper on all driven shafts may further reducevibratory transmission to belt tensioner 142 and engine frame 112.

While the invention has been disclosed and described in some detail inthe drawings and foregoing description, they are to be considered asillustrative and not restrictive in character, as other modificationsmay readily suggest themselves to persons skilled in the art and withinthe broad scope of the invention. The invention includes allmodifications encompassed within the spirit and scope of the followingclaims.

What is claimed is: . .1. The combination comprising: therebetween..!.2.The combination as claimed in claim . .1.!. .Iadd.5 .Iaddend.whereinsaid resilient member comprises an input end and an output end, saidinput end being fixed to said mounting element and said output end beingfixed to said driving pulley, said resilient member extending radiallyoutward from said input end towards said output end. . .3. Thecombination as claimed in claim 1 further comprising a mass elementannularly disposed about said output shaft for further damping saidbending and torsional vibrations of said output shaft..!.4. Thecombination as claimed in claim . .3.!. .Iadd.5 .Iaddend.furthercomprising an annular retaining element fixed to said mounting elementfor retaining said mass element in a radially spaced, concentricposition about said mounting element.
 5. The combination . .as claimedin claim 3,.!. .Iadd.comprising:an internal combustion engine includingan engine frame and an output shaft rotatable by operation of saidinternal combustion engine, said output shaft being subject to torsionaland bending vibrations resulting from rotation thereof in conjunctionwith the operation of said internal combustion engine; a plurality ofdriven shafts mounted for rotational movement about parallel axes fixedwith respect to said engine frame; a plurality of driven pulleys, eachof said driven pulleys operatively connected with a corresponding one ofsaid driven shafts; a driving pulley for said output shaft; an endlessflexible poly-V belt trained about said driven and said driving pulleys,said poly-V belt being subject to transitional vibrations from changingrotational speeds of said output shaft; a belt tensioner carried by theengine frame in tensioning engagement with said poly-V belt formaintaining said poly-V belt in driven engagement with said drivingpulley and in driving engagement with said driven pulleys; and avibration damper assembly operatively connecting said driving pulleywith said output shaft for damping said torsional vibrations, saidbending vibrations, and said transitional vibrations transmitted fromsaid output shaft through said poly-V belt and said engine frame to saidbelt tensioiner, said vibration damper assembly comprising a mountingelement, fixed to said output shaft, in torsional transmitting relationtherewith; bearing means operatively disposed between said drivingpulley and said mounting element to restrict relative movementtherebetween to torsional relative movement; a resilient memberoperatively connected between said driving pulley and said mountingelement in resilient torsional transmitting relation therebetween; amass element annularly disposed about said output shaft for damping saidbending and torsional vibrations of said output shaft; and.Iaddend.wherein said mass element is fixed to said mounting element through anelastic damping element.
 6. The combination as claimed in claim 4wherein said mass element is connected to said annular retaining elementvia . .an.!. .Iadd.said .Iaddend.elastic damping element.
 7. Thecombination as claimed in claim . .1.!. .Iadd.5 .Iaddend.wherein saidresilient member is comprised of rubber.
 8. The combination as claimedin claim 6 wherein said elastic damping element is comprised of rubber.9. The combination as claimed in claim . .1.!. .Iadd.5 .Iaddend.furthercomprising a back-up means for providing torsional transmission betweensaid mounting element and said driving pulley in the event saidresilient member fails in said torsional transmission.
 10. Thecombination as claimed in claim 7 . .wherein said.!. .Iadd.having.Iaddend.back-up means .Iadd.that .Iaddend.comprises:at least oneprotruding portion disposed on said mounting element and a correspondingedge surrounding a slot in said driving pulley, said protruding portionprotruding through said slot in a spatially separated relation to saidedge, said resilient member impeding relative rotational movementbetween said driving pulley and said mounting element so as to impedesaid protruding . .member.!. .Iadd.portion .Iaddend.from engaging saidedge when said resilient member is in proper torsional transmittingrelation between said mounting element and said driving pulley, saidprotruding . .member.!. .Iadd.portion .Iaddend.being able to engage saidedge when said resilient member fails to be in said proper torsionaltransmitting relation so that said back-up means is in torsionaltransmitting relation between said mounting element and said drivingpulley.
 11. The combination as claimed in claim . .1.!. .Iadd.5.Iaddend.further comprisingat least one accessory vibration damperassembly, each said accessory vibration damper assembly operativelyconnecting one of said driven pulleys with said corresponding one ofsaid driven shafts, each said accessory vibration damper assemblydamping torsional vibrations, bending vibrations, and transitionalvibrations transmitted from said corresponding one of said driven shaftsthrough said poly-V belt and said engine frame to said belt tensioner,each said accessory vibration damper assembly comprising a drivenmounting element; fixed to said corresponding one of said driven shaft,in torsional transmitting relation therewith; driven bearing meansoperatively disposed between said one of said driven pulleys and saiddriven mounting element to restrict relative movement therebetween totorsional relative movement; and a driven resilient member operativelyconnected between said one of said driving pulleys and said drivenmounting element in resilient torsional transmitting relationtherebetween.
 12. The combination comprising:an internal combustionengine including an engine frame and an output shaft rotatable byoperation of said internal combustion engine, said output shaft beingsubject to torsional vibrations and bending vibrations resulting fromrotation thereof in conjunction with the operation of said internalcombustion engine; a plurality of driven shafts mounted for rotationalmovement about parallel axes fixed with respect to said engine frame, aplurality of driven pulleys, each of said driven pulleys operativelyconnected to a corresponding one of said driven shafts; a drivingpulley-for said output shaft; an endless flexible poly-V belt trainedabout said driven and driving pulleys, said poly-V belt being subject totransitional vibrations from rotational speeds of said output shaft; abelt tensioner carried by the engine frame, said belt tensionercomprising: (1) a fixed structure fixed with respect to said engineframe, (2) a movable structure mounted on said fixed structure formovement in one plane (3) a pulley element mounted on said movablestructure for rotational movement about a rotational axis, and (4)biasing means for resiliently biasing said movable structure in adirection in said plane toward said poly-V belt for maintaining saidpulley element in rotational tensioning engagement with said poly-V beltand for maintaining said poly-V belt in driven engagement with saiddriving pulley and in driving engagement with said driven pulleys, saidmovable structure being subject to oscillatory movement with respect tosaid fixed structure as a result of said torsional vibrations, saidbending vibrations, and said transitional vibrations being transmittedto said movable structure from said output shaft through said poly-Vbelt and said engine frame; and damping means for damping saidoscillatory movement of said movable structure, said damping meanscomprising: a mounting element, fixed to said output shaft, in torsionaltransmitting relation therewith; bearing means operatively disposedbetween said driving pulley and said mounting element to restrictrelative movement therebetween to torsional relative movement; and aresilient member operatively connecting said driving pulley and saidmounting element in resilient torsional transmitting relationtherebetween.
 13. The combination as claimed in claim 12 wherein saidresilient member comprises an input end and an output end, said inputend being fixed to said mounting element and said output end being fixedto said driving pulley, said resilient member extending radially outwardfrom said input end towards said output end.
 14. The combination asclaimed in claim 12 . .further comprising.!. .Iadd.wherein .Iaddend.amass element .Iadd.of the damping means is .Iaddend.annularly disposedabout said output shaft for damping torsional and bending vibrations ofsaid output shaft.
 15. The combination as claimed in claim 14 furthercomprising an annular retaining element fixed to said mounting elementfor retaining said mass element in a radially spaced; concentricposition about said mounting element.
 16. The combination as claimed inclaim 15 wherein said mass element is connected to said annularretaining element via an elastic damping element .Iadd.of the dampingmeans..Iaddend.17. The combination as claimed in claim 12 wherein saidresilient member comprises a rubber material.
 18. The combination asclaimed in claim 16 wherein said elastic damping element comprises arubber material.
 19. The combination as claimed in claim 12 furthercomprising a back-up means for providing torsional transmission betweensaid mounting element and said driving pulley in the event saidresilient member fails in said torsional transmission.
 20. Thecombination as claimed in claim 19, wherein said backup meanscomprises:at least one protruding portion disposed on said mountingelement and at least one corresponding edge surrounding a slot in saiddriving pulley, said protruding portion protruding through said slot ina spatially separated relation to said edge, said resilient memberimpeding relative rotational movement between said driving pulley andsaid mounting element so as to impede said protruding . .member.!..Iadd.portion .Iaddend.from engaging said edge when said resilientmember is in proper torsional transmitting relation between saidmounting element and said driving pulley, said protruding . .member.!..Iadd.portion .Iaddend.being able to engage said edge when saidresilient member fails to be in said proper torsional transmittingrelation so that said back-up means becomes in torsional transmittingrelation between said mounting element and said driving pulley.
 21. Thecombination as claimed in claim 12 further comprisingat least oneaccessory vibration damper assembly, each said accessory vibrationdamper assembly operatively connecting one of said driven pulleys withsaid corresponding one of said driven shafts, each said accessoryvibration damper assembly damping torsional vibrations, bendingvibrations, and transitional vibrations transmitted from saidcorresponding one of said driven shafts through said poly-V belt andsaid engine frame to said belt tensioner, each said accessory vibrationdamper assembly comprising a driven mounting element, fixed to saidcorresponding one of said driven shaft, in torsional transmittingrelation therewith; driven bearing means operatively disposed betweensaid one of said driven pulleys and said driven mounting element torestrict relative movement therebetween to torsional relative movement;and a driven resilient member operatively connected between said one ofsaid driving pulleys and said driven mounting element in resilienttorsional transmitting relation therebetween. .Iadd.22. The combinationaccording to claim 5, further comprising a mounting fastener constructedand arranged to fix said mounting element in mounted relation on saidoutput shaft;said mounting fastener having a head portion constructedand arranged to be engaged and manipulated by a tool; the combinationbeing constructed and arranged so as to be devoid of any obstructionthat would prevent movement of the tool in a direction parallel to anaxis of said output shaft or along the axis of said output shaft andinto engagement with the head portion of said mountingfastener..Iaddend..Iadd.23. The combination comprising: an internalcombustion engine including an engine frame and an output shaftrotatable by operation of said internal combustion engine, said outputshaft being subject to torsional and bending vibrations resulting fromrotation thereof in conjunction with the operation of said internalcombustion engine; a plurality of driven shafts mounted for rotationalmovement about parallel axes fixed with respect to said engine frame; aplurality of driven pulleys, each of said driven pulleys operativelyconnected with a corresponding one of said driven shafts; a drivingpulley for said output shaft; an endless flexible poly-V belt trainedabout said driven and said driving pulleys, said poly-V belt beingsubject to transitional vibrations from changing rotational speeds ofsaid output shaft; a belt tensioner carried by the engine frame intensioning engagement with said poly-V belt for maintaining said poly-Vbelt in driven engagement with said driving pulley and in drivingengagement with said driven pulleys; and a vibration damper assemblyoperatively connecting said driving pulley with said output shaft fordamping said torsional vibrations, said bending vibrations, and saidtransitional vibrations transmitted from said output shaft through saidpoly-V belt and said engine frame to said belt tensioiner, saidvibration damper assembly comprising a mounting element, fixed to saidoutput shaft, in torsional transmitting relation therewith; a masselement annularly disposed about an axis of said output shaft and fixedto said mounting element via an elastic damping element; bearing meansoperatively disposed between said driving pulley and said mountingelement to restrict relative movement therebetween to torsional relativemovement; a resilient member operatively connected between said drivingpulley and said mounting element in resilient torsional transmittingrelation therebetween; and wherein an axial extent of said poly-V beltalong the axis of said output shaft is axially overlapped with at leasta portion of the mass element, at least a portion of the elastic dampingelement, and at least a portion of the resilientmember..Iaddend..Iadd.24. The combination in claim 23, wherein an axialextent of said bearing means is axially overlapped with at least aportion of said mass element and at least a portion of said elasticdamping element..Iaddend..Iadd.25. The combination in claim 23, whereinsaid axial extent of said bearing means is axially overlapped with atleast a portion of said poly-V belt..Iaddend..Iadd.26. The combinationas claimed in claim 23, further comprising a fastening structureconstructed and arranged to mount said vibration damper assembly on saidoutput shaft, wherein said mounting element has a fastener bearingsurface constructed and arranged to receive force which is appliedaxially inwardly with respect to said output shaft when said fasteningstructure is tightened to mount the vibration damper assembly on saidoutput shaft;said poly-V belt having at least a portion of its axialextent positioned further axially inwardly relative to the axialposition of said fastener bearing surface..Iaddend..Iadd.27. Thecombination comprising:an internal combustion engine including an engineframe and an output shaft rotatable by operation of said internalcombustion engine; a plurality of driven shafts mounted for rotationalmovement about parallel axes fixed with respect to said engine frame; aplurality of driven pulleys, each of said driven pulleys operativelyconnected with a corresponding one of said driven shafts; a drivingpulley for said output shaft; an endless flexible poly-V belt trainedabout said driven and said driving pulleys; a belt tensioner carried bythe engine frame in tensioning engagement with said poly-V belt formaintaining said poly-V belt in driven engagement with said drivingpulley and in driving engagement with said driven pulleys; and avibration damper assembly operatively connecting said driving pulleywith said output shaft comprising: a mounting element; a mass elementannularly disposed about an axis of said output shaft and fixed to saidmounting element via an elastic damping element; bearing meansoperatively disposed between said driving pulley and said mountingelement to restrict relative movement therebetween to torsional relativemovement; and a resilient member operatively connected in radiallyextending relation relative to said axis of said output shaft betweensaid driving pulley and said mounting element, said resilient memberbeing disposed in radially resilient torsional transmitting relationbetween said mounting element and said driving pulley; wherein saidmounting element is constructed and arranged to mount said drivingpulley, said mass element, said elastic damping element, said bearingmeans, and said resilient member as a unitary assembly on said outputshaft; and wherein an axial extent of said poly-V belt alone the axis ofsaid output shaft is axially overlapped with at least a portion of themass element, at least a portion of the elastic damping element, and atleast a portion of the resilient member..Iaddend..Iadd.28. Thecombination in claim 27, wherein an axial extent of said bearing meansis axially overlapped with at least a portion of said mass ring and atleast a portion of said elastic damping element..Iaddend..Iadd.29. Thecombination in claim 27, wherein said axial extent of said bearing meansis axially overlapped with at least a portion of said poly-V belt..Iadd.30. The combination as claimed in claim 27, further comprising afastening structure constructed and arranged to mount said vibrationdamper assembly and driving pulley on said output shaft, wherein saidmounting element has a fastener bearing surface constructed and arrangedto receive force which is applied axially inwardly with respect to saidoutput shaft when said fastening structure is tightened to mount thevibration damper assembly on said output shaft;said poly-V belt havingat least a portion of its axial extent positioned further axiallyinwardly relative to the axial position of said fastener bearingsurface..Iaddend..Iadd.31. The combination as claimed in claim 27,wherein said resilient member comprises an input end and an output end,said input end being fixed to said mounting element and said output endbeing fixed to said driving pulley, said resilient member extendingradially outward from said input end towards said outputend..Iaddend..Iadd.32. The combination according to claim 27, whereinsaid elastic damping element is disposed in generally radially extendingrelation with respect to said axis of said output shaft and primarilydampens bending vibrations..Iaddend..Iadd.33. The combination accordingto claim 27, wherein said elastic damping element is disposed ingenerally axially extending relation with respect to said axis of saidoutput shaft and primarily dampens torsional vibrations..Iaddend.